The future might be portability, but it's not clear if Java will be there.

It's quite easy to write portable programs with Perl, and it's at least as easy to write stuff that's horribly unportable with Java. I know of OpenGL-wielding, native-sound-library-calling multimedia demos written in Java that only run under Internet Explorer 4+ with the Microsoft JVM, and I know of programs written in Perl that work on any platform.

Programming languages are not portable, programs are.

If you anticipate enough of your programs needs and know how to encapsulate the facilities, porting will be easy, maybe as easy as "copy the code". If you use modules, or in the case of java, use any external (native or Java) libraries, you create dependencies. You have to see yourself how much increased dependencies weigh against the speed gain in development.